Sound

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Sound and the NVH Team
2005 FSR / DSS Conference Terry Ryan Mike
Yost
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Sound Fundamentals

• To have Sound 3 things must exist
• A source
• A path
• A receiver

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Airborne sound will travel outward from its source
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Sound reflecting off a structure will double
Wall of structure.
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Wall or Fence.
Wall of structure.
Sound reflecting off these structures will
virtually quadruple
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Structure Born Sound

1. Transmitted from the SOURCE through a SOLID
   Object
2. Structure acts like a Speaker
3. Structure borne sound can be audible throughout a
   room

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Airborne SoundWAA-WAA

1. Compressors having a synchronous speed of 3600
   RPM (and loaded around 3300 to 3400 RPM)
2. The outdoor fan motor having a synchronous speed
   of 1200 (loaded near 1100). Multiply the number
   of blades on the fan (3) and we get its
   frequency of 3300.
3. The difference between the fan and compressor
   frequencies cause the beating waa-waa sound.

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Airborne SoundWAA-WAA
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Airborne SoundWAA-WAA
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Airborne SoundPlatform Acts Like Megaphone
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Structure Borne Sound
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Structure Borne Sound
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Structure Borne Sound
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Hydraulic Hammer
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Damaged Internal Springs
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Damaged Internal Springs
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Stethoscope Looking for source of sound
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NVH Field VisitFiltered Beats Complaint

• 2/15/2005
• Dave Renegar, Rick St. Mars, Jerry Hoover

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Line Set runs up wall into attic 1-1/8 3/8
Master Bed Room on other side of wall (Where
sound is objectionable)
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Hard 90 brazed in-between brick wall stud space
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• First attempt by Installer
• Compressor replaced once

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• ISR0063 added inside unit and outside unit
• Removed mortar from contact with line set